Romney has the support of 51 percent of married voters compared with 38 percent for Obama. Unmarried voters side with Obama 54 percent to 34 percent.

In both categories Obama performs stronger among women than men, but the support of single women is particularly pronounced, by a 2-to-1 margin.

Quinnipiac’s Peter Brown says the marriage gap could be attributed to the “different priorities and economic situations” of the two groups — married people tended to be older and more financially secure, and the sample was more Republican and white.

Also, “married voters are more likely to focus on the economy and health care, while single voters are more focused on issues such as gay rights and reproductive issues,” Brown said.

In 2008 Obama won 56 percent of the vote of women with no children, compared to 43 percent for John McCain, according to exit polls. Married mothers went for Obama 51 percent to 47 percent, and all other women went for the Democrat 58 percent to 40 percent.

The Obama campaign is making a major play for the women’s vote in key states like Virginia, where a new campaign advertisement says “every woman who believes decisions about our bodies and our health care should be our own is troubled Mitt Romney supports overturning Roe vs. Wade.” It also quotes Romney as saying he would cut off funding to Planned Parenthood.

Overall, voters give Obama a negative rating for his handling of the economy — 55 percent disapprove, while just 40 percent approve. But Romney has just a 1-point advantage on the question of which candidate would do a better job on the economy.

Independent voters back Romney 43 percent to 41 percent, while Republicans and Democrats each overwhelmingly support their respective candidate.